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Changing Climate Numbers

In 2007, the Intergovernmental Panel on Climate Change released its fourth assessment report, summarizing evidence collected and weighed by scientists around the world. At the time, it was the best estimate of where the planet was, climatically speaking, and where it was likely to be going, and the news the report offered was daunting.

There was unequivocal evidence of a warming climate, with human activity the dominant cause. The panel warned that further warming could have devastating consequences for societies around the world, including rising seas and widespread drought.

The 2007 assessment established a base line of expectation, but it is already looking outdated. From all over the globe, in bits and pieces, data are accumulating that suggest we may have already left behind the world of possibilities portrayed in the panel’s report. Sea ice has melted more quickly than expected. And, according to a recent report from the United States Geological Survey, sea levels in 2100 could increase by more than double the 1.5 feet rise projected by the Intergovernmental Panel on Climate Change (it chose not to add in water from eroding ice sheets because they remain poorly understood). Add to that the hard reality that carbon dioxide is a long-lived gas, and the picture of global warming is both volatile and forbidding.

The authors of the climate-change panel’s report knew that events could overtake their findings. A fifth assessment is currently under way. And while the worldwide recession might provide a slight breather, population pressures and energy demands are likely to drive emissions inexorably higher without a major shift to new energy sources.

It is imperative, of course, that the Obama administration — and every other government around the world — keep abreast of the changing data. What is equally imperative is that the governments tailor any prescriptions to the possibility of more ominous news in the future.

A version of this editorial appears in print on , on Page A20 of the New York edition with the headline: Changing Climate Numbers. Today's Paper|Subscribe